Why should athletes consume selenium-rich foods?
We explore this micronutrient, its functions and food sources.
Let us begin!
What Is Selenium?
Selenium is an essential mineral that must be obtained through food for normal vital functions.
Specifically, it is a trace element, needed only in small amounts.
What Does Selenium Do?
Selenium supports the thyroid gland and reproduction. It also contributes to immune function, protecting against infection.
It helps produce enzymes, a type of protein, with antioxidant functions that help prevent cell damage.
Selenium Properties
Which properties make selenium intake important?
- It supports proper immune function. It stimulates T-lymphocyte production and natural killer cell activity.
- It reduces viral infection virulence and progression in infections such as Coxsackievirus, poliovirus, hepatitis B and C, molluscum contagiosum poxvirus, influenza and HIV.
- It is essential for male and female fertility, associated with sperm motility and testosterone synthesis in men and reduced miscarriage risk in women.
- It influences mood and certain brain neurotransmitters. These mechanisms are associated with reduced incidence of depression, anxiety, confusion, hostility, epileptic seizures and Alzheimer’s disease.
- It protects against toxic effects of heavy metals and other harmful substances.
- It supports thyroid function. Selenium contributes to deiodinase production and regulation, promoting conversion of thyroid hormone T4 into active T3.
- It acts as an antioxidant and anti-inflammatory agent, with beneficial effects against rheumatoid arthritis, pancreatitis and asthma.
- It may protect against cardiovascular disease, although this role is not fully established.
- It may reduce the risk of some cancers. Appropriate selenium supplementation has been shown to reduce incidence and mortality in certain cancers under specific conditions, including leukaemia and cancers of the liver, colon, rectum, pancreas, breast, ovaries, prostate, bladder, lung and skin.
8 Selenium-Rich Foods
Where is this mineral found?
Here are some foods highest in selenium:
- Brazil nuts: 1,917 micrograms
- Tuna: 90 micrograms
- Oysters: 77 micrograms
- Mussels: 45 micrograms
- Sesame: 34 micrograms
- Eggs: 31 micrograms
- Brown rice : 23 micrograms
- White beans: 12.8 micrograms
- Coconut: 10 micrograms
- Brussels sprouts: 1.6 micrograms
Food selenium content depends on two factors:
- In plant foods , it depends on selenium in the soil where they grow.
- In animal foods , it depends on selenium in the animals’ feed.
How Do I Know If I Am Selenium-Deficient?
The margin between deficiency and excess is narrow.
Besides toxic effects from excessive selenium intake , known as selenosis, deficiency can cause male infertility and conditions such as Keshan disease , a heart disease, and Kashin-Beck disease , a type of arthritis causing joint pain, swelling and reduced mobility.
Subclinical deficiency may limit the expression of one or more antioxidant enzymes, with associated negative effects.
Blood concentration can indicate selenium status. Specifically:
- Deficiency is considered below 65 micrograms/L of blood.
- Normal values are considered between 60 and 90 micrograms/L of blood.
- Optimal values are considered between 90 and 140 micrograms/L of blood.
- Possible side effects are considered above 250 micrograms/L of blood.
- Toxicity is considered above 450 micrograms/L, and potentially fatal toxicity above 3,200 micrograms/L of blood.
Eating selenium-rich foods matters, but excessive blood levels can be dangerous.
How Much Selenium Do We Need?
Recommended intake depends on country and age. For Spain, daily recommendations are:
- Up to 6 months: 15 micrograms of selenium daily
- From 7 months to 3 years: 20 micrograms of selenium daily
- Ages 4 to 8: 30 micrograms of selenium daily
- Ages 9 to 13: 40 micrograms of selenium daily
- From age 14: 55 micrograms of selenium daily
- During pregnancy: 60 micrograms of selenium daily
- During breastfeeding: 70 micrograms of selenium daily
Selenium and the Thyroid: What Is the Connection?
Proper thyroid function requires iodine and other nutrients, including selenium, iron, zinc, copper and calcium.
Regarding selenium, the thyroid gland contains more than any other organ.
Thyroid hormones are released as T4 and T3 , the latter more active and potent. The thyroid secretes only 20% of T3. The remaining 80% of T3 comes from conversion of T4 to T3 through deiodinase enzymes, where selenium plays a role.
Selenium is essential for the activity of the deiodinase enzyme because it contains the amino acid selenocysteine. Adequate intake therefore supports proper thyroid hormone activity.
Why Are Selenium and Zinc Often Recommended Together?
Supplementation often combines selenium + zinc because they form an antioxidant complex. Their functions complement, support and protect one another, producing a synergistic effect.
Are There Foods Containing Selenium and Zinc?
Yes. Foods combining both include walnuts and other nuts, pumpkin seeds, oats, rice and wholemeal bread.
Selenium in an Athlete’s Diet
The main sporting interest in selenium concerns post-exercise recovery.
Exercise increases oxidative stress and free radicals. Adequate selenium increases glutathione peroxidase, an enzyme protecting against oxidative stress.
Around 11% of athletes may have selenium deficiency . Currently, detrimental effects are associated with selenium deficiency or excess.
An excess of selenium may impair performance by causing excessive mitochondrial stress , damaging cellular organelles and their function.
Appropriate intake of selenium-rich foods may therefore help reduce chronic exercise-related oxidative stress.
There appears to be no performance benefit from selenium supplementation , which would only be recommended in deficiency.
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